The written expression of an
idea is not achieved only through the simple combination of the different
components of the grammar based on a given syntax. Other factors take part in
the process, such as semantics and context. But it is obvious that a first
approach requires at least a correct syntactic analysis, and for this it is
necessary, from the computer-science point of view, to obtain results similar to
those obtainable by human knowledge. In this work, a first approach is achieved
by the identification and then disambiguation of the elements that are part of a
Traditionally, syntactic analysis requires a specialized
knowledge of the language, all the more so in the case of Spanish, due to its
wide range of variations which turn the syntactic analysis into a task only for
experts. From the educational point of view, syntactic analysis is very useful
to help learn to distinguish the different symbols implied: on the one hand, the
correct combination of the elements by means of the application of grammar
rules, and on the other hand, the incorporation of less tangible, although
necessary aspects, like semantics and context. People usually perform an
intuitive use that hides the true difficulty of the problem.
This system is intended to provide a close view of the
Spanish grammar to researchers, enhancing their performance and reliability.
This is a first step that will allow, with the addition of new features, to keep
improving until reaching100% accuracy. Any automated processing of a text
entails inevitably the syntactic analysis of its sentences, following the
morphosyntactic disambiguation of the elements that compose it, allowing for
different possible applications: a) to provide a precise synonymfor a given
word, b) to analyze its literary style, c) toreveal its semantics, d) to extract
information or summarize its contents, e) to make trustworthy translations to
other languages, f) to answer to concrete questions on its content, etc.
In this work, the number of
erroneous syntactic representation trees, obtained by the application of the
rules of the Spanish grammar by means of a set of structural disambiguation
rules, is notably reduced. In spite of the remarkable amount of necessary
combinations, this system does not limit itself to subgroups of the grammar like
most of the other proposals, but instead it uses a system of rules which covers
all the possible combinations of the Spanish grammar. In addition to being the
starting point for an automated syntactic analysis system, it complements the
local functional disambiguator developed by the Group of Data Structures and
Computational Linguistics of the University of Las Palmas de Gran Canaria(http://www.gedlc.ulpgc.es/investigacion/desambigua/desambigua.htm
As an indicator of its performance, theaccuracy of the disambiguation is raised
from 87% to 96%.
A solution is provided to the problem of the appearance of
structural ambiguities that are generated during the process of construction of
syntactic representation trees. The syntactic structures are combined to each
other to allow for the syntactic representation trees. Many of these
combinations generate erroneous trees. Direct conflicts between rules have been
identified as one of the main causes of the problem. The characteristics of the
different syntactic structures and how they must be considered at the time of
accepting or not the construction of a representation symbol have been studied
for the development of methods of structural disambiguation.
In view of the great number of possible combinations of the
grammar elements (more evident in verb-phrase constructions which allow any
number of elements and almost in any combination), the adequate representation
mechanisms have been defined so that all the possibilities are covered, not
leaving valid options unrepresented. When allowing any combination of possible
elements in the verb-phrase, some combinations appear, which should not be
allowed, and would be rejected in the structural disambiguation processes. In
this way, all the possible combinations are represented, from a structural point
of view, and those not allowed are rejected.
Groups of semantic identification oriented to the
recognition of syntactic structures are catalogued. The processes of structural
disambiguation include some rules that introduce semantic information. The
generated lists have been obtained from the tables of the ideological
dictionaries that can be related to certain syntactic structures.
The grammar used is based mainly
on the description made by Gili Gaya. To achieve maximum system completeness and
include all the syntactic structures that can appear we followed GutiÃ©rrez
Araus. The examplescited by GÃ³mez Torrego (2002a, 2002b), were useful to test
the system and contributed mainly to illustrate the aspects relative to the
compound sentences that remained to be refined.
For this work, the tagger developed by GEDLC was used (http://www.gedlc.ulpgc.es/investigacion/scogeme02/lematiza.htm
which gathers the main lexicographical repertoires of the Spanish
language, and admits 151103 canonical forms and something more
than 4900000 inflectioned and derived forms (without adding the inherent
extension to the prefixes and the enclitic pronouns that have also been
There are other authors that
approach this problem for the Spanish language from diverse points of view. In
the same way as our work, which can be used for free at discretion through the
we have only been able to find oneother operative tool of this kind on the
network: the parser from the Center of Language and Computing of the University
of Barcelona. Given the high complexity of the problem, they have chosen to
write down exclusively those elements that are explicitly present in the
sentence, which had led them to a simplified treatment of some syntactic aspects
like coordination and some subordinated types that they leave unsolved. Also,
they abandon the concept of sentence understood like noun-phrase and
verb-phrase, optingfor a list of components instead.
Although the computer methodologies applied are different,
they try to reach the same objectives. Our work is based on the real and
complete study of: a) a Spanish grammar that includes all the possibilities
available in the written language, b) the direct structural ambiguities that
cause the appearance of multiple syntactic representation trees, c) the symbols
that cannot cover all the sentence, d) the complex verbal form, e) other
situations where ambiguities can be solved based on linguistic knowledge about
words, grammar categories and objects involved, and f) the considerations for
the generation of the predicate symbol. Nevertheless, other methodologies apply
statistical criteria for the resolution of ambiguities, with the consequent loss
of reliability for unfrequent cases. The richness of our language and,
particularly, the writersâ€™ freedom in the construction of syntactic
structuresmakes usreconsider the probabilistic methods as the only solution to
this complex problem.
This work is not limited to
subsets of the grammar, but is based instead on a system of rules for the
Spanish grammar in spite of the remarkable quantity of necessary combinations.
It provides a solution to the problem of the appearance of
functional ambiguities. First a disambiguation process is applied, based on
local syntactic structures that reach an accuracy of 87%; and second, another
disambiguation process is applied, based on trees of syntactic representation
that improve the averageaccuracy level up to 96%.
The importance of this work lies on the fact that it
fosters the development of future applications, because:
- It accelerates the process of syntactic analysis when pruning incorrect
- It improves the precision in the results of advanced word searches.
- It allows the discarding of non valid options in information extraction.
- It detects grammatical errors in the written